kolt666 did not really feel up to maintaining this mod anymore, so i took over.

What

Ruins is a mod that spawns Structures in your Minecraft worlds upon generation, similar to Villages or Strongholds. Every Structure is defines by a template and configured to spawn under specific conditions, and all of that can be changed by you!

There is a lot of Structures already included, and there's bound to be more added.

You can export great structures you made using the new ingame template parser. See this instruction video here:

Loading the Tundra ruins templates...
Did not find any Building data for C:\Users\Person\AppData\Roaming\.minecraft\mods\resources\ruins\Tundra

There was an error when loading the Tundra ruins templates:
java.lang.IndexOutOfBoundsException: Index: 51, Size: 51
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.set(Unknown Source)
at RuinHandler.loadSpecificTemplates(RuinHandler.java:189)
at RuinHandler.<init>(RuinHandler.java:82)
at mod_Ruins.createHandler(mod_Ruins.java:102)
at mod_Ruins.checkWorld(mod_Ruins.java:57)
at mod_Ruins.generateSurface(mod_Ruins.java:43)
at ModLoader.populateChunk(ModLoader.java:1184)
at ko.a(ChunkProvider.java:204)
at ack.a(Chunk.java:1134)
at ko.c(ChunkProvider.java:113)
at ko.b(ChunkProvider.java:126)
at xd.d(World.java:636)
at xd.a(World.java:551)
at net.minecraft.client.Minecraft.e(Minecraft.java:2214)
at net.minecraft.client.Minecraft.a(Minecraft.java:2101)
at net.minecraft.client.Minecraft.a(Minecraft.java:2048)
at net.minecraft.client.Minecraft.a(Minecraft.java:1959)
at xh.a(SourceFile:163)
at vp.a(SourceFile:68)
at xh.a(SourceFile:233)
at vp.f(SourceFile:116)
at vp.i(SourceFile:104)
at net.minecraft.client.Minecraft.k(Minecraft.java:1584)
at net.minecraft.client.Minecraft.x(Minecraft.java:842)
at net.minecraft.client.Minecraft.run(Minecraft.java:747)
at java.lang.Thread.run(Unknown Source)

Loading excluded list from: C:\Users\Person\AppData\Roaming\.minecraft\saves\soa
No exclusions found for this world.

There was an error when loading the options file. Defaults will be used instead.
java.lang.ArrayIndexOutOfBoundsException: 51
at RuinHandler.readGlobalOptions(RuinHandler.java:260)
at RuinHandler.<init>(RuinHandler.java:106)
at mod_Ruins.createHandler(mod_Ruins.java:102)
at mod_Ruins.checkWorld(mod_Ruins.java:57)
at mod_Ruins.generateSurface(mod_Ruins.java:43)
at ModLoader.populateChunk(ModLoader.java:1184)
at ko.a(ChunkProvider.java:204)
at ack.a(Chunk.java:1134)
at ko.c(ChunkProvider.java:113)
at ko.b(ChunkProvider.java:126)
at xd.d(World.java:636)
at xd.a(World.java:551)
at net.minecraft.client.Minecraft.e(Minecraft.java:2214)
at net.minecraft.client.Minecraft.a(Minecraft.java:2101)
at net.minecraft.client.Minecraft.a(Minecraft.java:2048)
at net.minecraft.client.Minecraft.a(Minecraft.java:1959)
at xh.a(SourceFile:163)
at vp.a(SourceFile:68)
at xh.a(SourceFile:233)
at vp.f(SourceFile:116)
at vp.i(SourceFile:104)
at net.minecraft.client.Minecraft.k(Minecraft.java:1584)
at net.minecraft.client.Minecraft.x(Minecraft.java:842)
at net.minecraft.client.Minecraft.run(Minecraft.java:747)
at java.lang.Thread.run(Unknown Source)
Ruins mod loaded.

The game crashes occasionally, and from what I can tell it's only crashing when loading the tundra biome, although there may be a few more biomes causing the crash as well.

I believe this crash is caused because you have an array, which is hard coded to only take a maximum of fifty biomes. I would personally recommend either making the array dynamic, making it an ArrayList, or by making the default size around 100, instead of 50.